Urine Cast
Urinary Casts (Microscopic Examination)
Urinary casts are tiny tube-shaped structures formed inside the kidneys. A microscope can show whether they contain only protein or also blood cells and other material. The type helps explain the finding.
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What does finding casts mean?
A few hyaline casts, made mainly of protein, can appear without kidney disease. Casts containing cells or other material can point to a kidney problem. The word “casts” alone is not enough to interpret the result.
Check the type before the count
- A few hyaline casts
- Can occur with concentrated urine or exercise
- Cellular, waxy or other casts
- Need interpretation with kidney tests and symptoms
There is no single healthy cutoff for all casts. A count without the cast type should not receive a universal risk label. Reports often count casts per low-power field, written as /LPF.
Sources: MedlinePlus (NIH)
What can change this result?
What can explain the finding
- Concentrated urine or hard exercise can produce a few hyaline casts.
- Other cast types can point to kidney inflammation, infection or injury.
What to check on your report
- The type of cast matters more than a generic positive flag.
- How the sample was collected and how soon it was examined.
- Your creatinine, eGFR, urine protein and any symptoms.
There is no general diet or hydration fix for casts. Follow-up depends on the type and cause; do not stop a prescribed medicine without advice.
What should I do next?
- Look for the cast type on your report and ask the lab or clinician if it is missing.
- Review the finding with creatinine, eGFR and the other urine results.
- Follow the collection instructions for any repeat sample. Do not stop medicines or force extra fluids just to change this result.
How this test works
Casts take the shape of the kidney tubes where they form. Material caught inside them gives clues about what is happening in the kidneys. That makes their appearance more informative than a count alone.